GB1600986A

GB1600986A - Road marking method

Info

Publication number: GB1600986A
Application number: GB30476/77A
Authority: GB
Original assignee: PREFORMED ROAD MARKINGS Ltd
Current assignee: PREFORMED ROAD MARKINGS Ltd
Priority date: 1977-07-20
Filing date: 1977-07-20
Publication date: 1981-10-21
Also published as: AU3792778A; DE2831386A1; SE7807970L; IT7850369A0; FR2398143A1

Description

(54) IMPROVED ROAD MARKING METHOD (71) We, PREFORMED ROAD MARKINGS LIMITED, of 8 Bolton Street, London, W1Y 8AU, a British Company, hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention is concerned with improvements in and relating to road marking.

Various methods are known for marking road surfaces, for example with contiguous or broken white or yellow lines. Some methods involve the use of rigid performed plastics markings which are attached to the road surface with adhesive. In one method the undersurface of the plastics marking is treated with adhesive from one half of a two-pack epoxy resin adhesive mix, and the road surface which is to receive the plastics marking is treated with the other half of the pack. The coated surfaces are brought together under compression to bond the mark to the road. The material most commonly used is rigid P.V.C. sheeting, already known for surfacing pedestrian crossings. In another method heat may be used as well as adhesive to apply the marking to the road surface.

Another method, perhaps most widely used to lay single or double white or yellow lines on motorways and trunk roads, involves the use of a road marking thermoplastic material which already contains the necessary pigments to contrast with the colour of the existing road surface. Blocks of the thermoplastic material are melted down at the road marking site and molten thermoplastic is sprayed out under pressure to form the desired lines on the road surface. By use of suitable mechanical controls of the spray, the widths and lengths of the lines can be determined.

The problem with the former methods involving preformed road markings is that a very high compression is required to ensure satisfactory bonding and the process is consequently an expensive one because of the expensive material and relatively sophisticated adhesives needed. Also any movement in the asphalted road surface causes the P.V.C to crack and break away. On the other hand the thermoplastic material which is laid molten is fairly easy to lay. The drawbacks of this method are the cost of the lorry, and the relatively thin layer which is sprayed, which is easily worn away by heavy traffic.

The screed-applied road marking method offers the best advantages over those already described. In this method the same molten road marking thermoplastic material, made in accordance with British Standard Specification No. 3262, as is used in the second method is melted down on site and laid hot on the road within special templates or chalk markings.

The life expectancy of markings made in this way is high, because inevitably a reasonable thickness of material is deposited on the road. However the process is cumbersome and some trimming often has to be done. The markings can also be laid too thickly which results in premature chipping and cracking under heavy traffic.

If the same material were used in a pre-set condition and laid on the road as a preformed marking. the marking would be too brittle to handle effectively without cracking at normal temperatures. On the other hand if further oil of the sort already used to plasticise the material were added it would remain in the marking after bonding to the road so that the marking could be handled, but would then be too soft to be an effective and useful road marking when laid on the road surface.

According to the present invention there is provided a method of manufacturing a preformed road marking for laying on the surface of a road, the method comprising the steps of taking a thermoplastic material which, if laid on the surface in a molten state would produce a satisfactory road marking, and heating said material with an additive to produce sufficient further resilience to facilitate handling of the marking without it cracking before the marking is laid on the road, the additive being substantially removeable from the marking by the application of heat during the laying thereof; forming the heated mixture into a desired shape, and allowing it to set.

The road marking may be formed into, for example, an individual strip, a continuous line, a letter, or a shaped direction indicating symbol.

Preferably the thermoplastic material is a mixture containing aggregate, pigment, extender and thermoplastic binder. Vegetable oil may be used as the additive.

It is advantageous to form the heated mixture into the desired shape by pouring the mixture to form a sheet and cutting the required shape from the sheet while it is still hot.

The invention also provides a preformed road marking comprising a set mixture of a thermoplastic material which, if laid on the road surface in a molten state would produce a satisfactory marking and an additive which produces sufficient further resilience to facilitate handling of the marking without it cracking before the marking is laid on the road, the said additive being capable of being removed from the marking by the application of heat during the laying thereof.

The invention further includes a method of road marking wherein a preformed marking according to the immediately preceding paragraph is heat bonded to the road surface without the addition of adhesive between the marking and the road surface. The heat applied to the marking should be sufficient to burn off the additive without distorting the marking, thus removing the additive from the marking. Any additive that is not removed in this way will be removed by compression in use by traffic.

The road marking may be heat bonded to the road surface either by first laying it in position on the road surface and then applying heat from above, or alternatively by first heating the road marking from beneath, then laying it on the road and pressing it to the road surface to obtain an immediate hot bond.

The present invention will now be described by way of example.

To produce a road marking in accordance with the invention, a block of thermoplastic material is heated in a vat with an additive suitable to remove the brittleness from a set layer of thermoplastic and leave it with sufficient pliability to resist chipping and cracking, and to be handled reasonably at normal temperatures, without rendering the thermoplastic marking incapable of subsequent satisfactory bonding with the road surface.A suitable thermoplastic material is disclosed in British Standard Specification No. 3262, to which the reader's attention is directed, and may comprise the following constituents: Constituent Percentage by mass of total mixture Minimum Maximum Binder (resin and oil) 18 22 Pigment 6 Pigment and extender 18 22 Reflective particles 20 - Aggregate, pigment extender and reflective 78 82 particles The aggregate can be for example silica sand, quartz or flint. The extender is a powder which helps the dispersion of the pigment, and the binder is a thermoplastic resinous material, such as synthetic hydrocarbon resin, or rosin, which has mineral oil added to it.

The mineral oil incorporated in the mixture dissolves in the mixture and remains in the marking when laid to improve the resilience.

Vegetable oil has been found to be a suitable additive for adding to a mixture, such as the above defined thermoplastic material. The vegetable oil remains globular when added to the mixture, rather than dissolving, and will burn off when the marking is laid by heat application, so that it need not effect the resilience of the laid marking.It is thought that other plasticisers or rubberisers might have a similar effect, and the following could be tried: Rubberisers i) Butadiene CFj=CH-CH=CH2 ii) Isoprene CH2=C-CH(CH3)=CH2 iii) Chloroprene CH2=CH-C-Cl=CH2 Plasticisers i) Tricresyl phosphate ii) Dioctyl phthalate iii) Dibutyl sebacate iv) Polymetric adipate-laurate The melted mixture is then moulded or poured into the shape required, which may be a continuous line, a strip, a letter or a shaped direction indicating symbol; or alternatively the melted mixture may be poured into a sheet from which the required shape can be cut or stamped. The thickness of the sheet or marking can be adjusted according to requirements.

Road markings so formed can be produced under controlled conditions at a site well removed from the road marking site, packaged and stored to await delivery to a road marking site.

When a road is to have new markings, preformed markings are delivered to the site.

These are laid down on the road surface in the correct position and heat-bonded to the road surface by playing a hot jet over the line of markings.

The thermoplastic material would normally incorporate reflective glass particles, and these will automatically be incorporated in the final pre-formed marking. However it has been found that the heating of the material with the additive, followed by subsequent pouring and setting tends to cause the integral glass particles to settle down in the bottom region of the marking. When the marking is laid on the road surface thereof, a layer of reflective glass particles can be applied to the surface of the heated markings. This gives reflectability to the markings during the initial period when traffic is passing over them. By the time this top layer of reflective glass particles has worn away, the marking itself has been worn down sufficiently to expose the integral particles.

If it is subsequently desired to alter the markings on the road, or to obliterate them altogether, the markings can readily be stripped off the road after suitable preparator treatment without unduly damaging the road surface itself. There is then no danger of the markings re-appearing on the road surface, as would be the case if they had had to be overpainted rather than being removed.

For laying single or double lines along extensive stretches of roadway, lines preformed as described above can be coiled onto a mechanical dispenser. The dispenser feeds out the coiled line, which can either be laid down on the road surface and heated from above, or alternatively heated from beneath as it comes off the back of the dispenser and then pressed down on the road surface to obtain an immediate hot-bond. The dispenser could easily be fitted to an existing lorry, travelling along the road surface and steadily uncoiling the pre-formed line or lines.

Example As an experiment, one particular road marking symbol was produced as follows: A block of road marking thermoplastic material made in accordance with British Standard Specification 3262 was heated in a vat with approximately 1/2% by weight of vegetable oil. When the heated mixture had melted in the vat, it was poured on to a bed of water-saturated rubber from which the surplus water had been wiped off. The watersaturated rubber sheet presented a flat surface for receiving the poured material, and the rubber sheet was contained in a tray having relatively shallow side walls so that the poured material settled out within the confines of the tray.

Silicone-impregnated paper was laid over the top surface of the still warm material after it had initially settled out over the rubber sheet. The paper was laid with the silicone film facing outwardly of the thermoplastic material, and enabled the material to be rolled out flat without the roller sticking to the material itself. In this way a layer approximately 1.5mm thick was obtained, and was allowed to set.

When the material had set, the rubber sheet together with the material and the silicone-impregnated paper were transferred into a bath of water. This allowed the already water-saturated rubber to be peeled off one face of the material, and the siliconeimpregnated paper to be peeled off the other surface as the silicone effectively transferred from one side of the paper to the other.

The thin sheet of set material so obtained is resilient to a limited degree at normal ambient temperatures. From this sheet, a series of letters forming the word SLOW was cut to precisely predetermined size and shape.

To use these letters in a method embodying the invention, the letters were transported at a later date to the road surface which needed to be marked. The four letters forming the word SLOW were then simply laid in position on the road surface, an ordinary blow torch was played over them very rapidly and then removed, and it was found that all four letters, when cool, had bonded to the road surface.

It is envisaged that a hot air jet from a machine designed to lay road markings in this way might also be used. The mixture of thermoplastic and additive which forms the marking has a melting point of about 1500C whereas the most intense part of a blow torch flame is typically at a temperature of about 450"C. There is clearly a danger of burning through the marking if the blow torch is used for too long. Care should therefore be taken when applying heat to the marking to avoid burning or distorting the marking itself.

WHAT WE CLAIM IS: 1. A method of manufacturing a preformed marking for laying on the surface of a road, the method comprising the steps of taking a thermoplastic material which, if laid on the surface in a molten state would produce a satisfactory road marking, and heating said material with an additive to produce sufficient further resilience to facilitate handling of the marking without it cracking before the marking is laid on the road, the additive being substantially removeable from the marking by the application of heat during the laying thereof; forming the heated mixture into a desired shape and allowing it to set.

2. A method according to claim 1 wherein the thermoplastic material comprises a mixture of aggregate, pigment, extender and a thermoplastic binder.

3. A method according to claim 1 or 2 wherein the additive is vegetable oil.

4. A method according to claim 1 or 2 wherein the additive is selected from the following: butadiene; isoprene; chloroprene; tricresyl phosphate; dioctyl phthalate; dibutyl sebacate; and polymetric adipate laurate.

5. A method according to any of claims 1 to 4 wherein the amount of the additive used is substantially l/2% by weight of the thermoplastic material.

6. A method according to any of the preceding claims wherein the shape of the marking is selected from the group consisting of an individual line, a continuous line, a letter, and a shaped direction indicating symbol.

7. A method according to any of the preceding claims wherein the heated mixture is formed into the desired shape by pouring the mixture into a sheet and cutting the shape from the sheet.

8. A method of manufacturing a preformed road marking substantially as herein described with reference to the example.

9. A preformed road marking comprising a set mixture of a thermoplastic material which, if laid on the road in a molten state would produce a satisfactory road marking, and an additive which produces sufficient further resilience to facilitate handling of the marking without cracking before the marking is laid on the road, the said additive being capable of being removed from the marking by the application of heat during the laying thereof.

10. A preformed marking according to claim 9 wherein the thermoplastic material comprises a mixture of aggregate, pigment, extender and a thermoplastic binder.

11. A preformed marking according to claim 9 or 10 wherein the additive is vegetable oil.

12. A preformed marking according to claim 9 or 10 wherein the additive is selected from the following: butadiene; isoprene; chloroprene; tricresyl phosphate; dioctyl phthalate, dibutyl sebacate; and polymetric adipate laurate.

13. A preformed marking according to any of claims 9 to 12 wherein the amount of the said additive used is substantially l/2% by weight of the thermoplastic material.

14. A preformed road marking substantially as herein described with reference to the example.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. material settled out within the confines of the tray. Silicone-impregnated paper was laid over the top surface of the still warm material after it had initially settled out over the rubber sheet. The paper was laid with the silicone film facing outwardly of the thermoplastic material, and enabled the material to be rolled out flat without the roller sticking to the material itself. In this way a layer approximately 1.5mm thick was obtained, and was allowed to set. When the material had set, the rubber sheet together with the material and the silicone-impregnated paper were transferred into a bath of water. This allowed the already water-saturated rubber to be peeled off one face of the material, and the siliconeimpregnated paper to be peeled off the other surface as the silicone effectively transferred from one side of the paper to the other. The thin sheet of set material so obtained is resilient to a limited degree at normal ambient temperatures. From this sheet, a series of letters forming the word SLOW was cut to precisely predetermined size and shape. To use these letters in a method embodying the invention, the letters were transported at a later date to the road surface which needed to be marked. The four letters forming the word SLOW were then simply laid in position on the road surface, an ordinary blow torch was played over them very rapidly and then removed, and it was found that all four letters, when cool, had bonded to the road surface. It is envisaged that a hot air jet from a machine designed to lay road markings in this way might also be used. The mixture of thermoplastic and additive which forms the marking has a melting point of about 1500C whereas the most intense part of a blow torch flame is typically at a temperature of about 450"C. There is clearly a danger of burning through the marking if the blow torch is used for too long. Care should therefore be taken when applying heat to the marking to avoid burning or distorting the marking itself. WHAT WE CLAIM IS:

1. A method of manufacturing a preformed marking for laying on the surface of a road, the method comprising the steps of taking a thermoplastic material which, if laid on the surface in a molten state would produce a satisfactory road marking, and heating said material with an additive to produce sufficient further resilience to facilitate handling of the marking without it cracking before the marking is laid on the road, the additive being substantially removeable from the marking by the application of heat during the laying thereof; forming the heated mixture into a desired shape and allowing it to set.

3. A method according to claim 1 or 2 wherein the additive is vegetable oil.

15. A method of marking a road surface wherein a preformed road marking according

to any of claims 9 to 14 is heat bonded to the road surface to cause the marking to adhere to the surface and the additive to be substantially removed.

16. A method according to claim 15 wherein the marking is heat bonded to the road surface by first laying the marking in position on the road and then applying heat from above.

17. A method according to claim 16 wherein the heat is applied from a blow torch.

18. A method according to claim 15 wherein the road marking is heated from beneath before it is laid on the road, and then pressed on the road surface to obtain a hot bond.

19. A method according to any of claims 15 to 18 wherein preformed road marking lines are laid on the road surface from a mechanical dispenser.

20. A method of road marking substantially as herein described with reference to the example.